You can't send the data over the serial port like that. Please read the LabVIEW documentation. The waveform datatype isn't just an array of values. It's more like a cluster. It contains a start time, a delta time, and an array of values. You only want the array of values. Thus, you need to use the Get Waveform Components to get just the array of values. But then, you seem to be getting multiple channels from the DAQ read, but your picture implies you only want one. So, which is it? If you're just getting one channel, then you should use the DAQ function that gets one channel, not the one that gets you multiple channels and returns an array of waveforms.
Furthermore, the Flatten to String function will prepend the size of the array to the flattened string. Unless the other end is expecting this, then you also do not want this. Again, this is in the LabVIEW documentation for the Flatten to String function.
Furthermore, you should not have the serial port initialization and close inside the loop. Why initialize the port each and every time? Initialize and close outside the loop.
